1. Field of the Invention
The invention relates to mast drive systems that extend, retract and rotate the mast particularly with respect to a submarine mast drive system. The system has particular application to a radar antenna mast.
2. Description of the Prior Art
The present day submarine radar system utilizes a radar antenna mounted near the top of an extendible and retractable mast. When utilizing the radar system, the mast is extended so that the antenna projects beyond the metal skin of the submarine and is then rotated to provide antenna scanning. Thereafter, the mast and antenna are retracted to within the outer periphery of the submarine for submerged running. Present day mast drive arrangements require utilization of two separate complex drive systems; viz, one system for mast extension and retraction and one system for mast rotation. For example, hydraulic cylinders or cable systems are utilized for extension and retraction and electrical gear drive systems are utilized for rotation. Such separate drive systems tend to be undesirably expensive and bulky and hence occupy large amounts of submarine space. Additionally, the requirements of compatibility between the rotational and translational systems tend to further exacerbate the system complexity and cost. Such systems also tend to require frequent maintenance during the expected life to overhaul cycles thereof.
In addition to the above disadvantages, prior art mast drive systems tend to generate undesirable noise levels such as hydraulic cylinder noise and noise generated from multiple complex gear systems. Prior art systems also often require complex and critical alignment procedures during mast installation, requiring external guides or alignment mechanisms attached to the submarine. Furthermore, in prior mast drive system designs, the extension mechanism bears the load of large portions of the systems with a concomitant reduction in reliability. Thus in prior designs, antenna drive unit equipment often loads the lower mast extension, resulting in an undesirable reduction in mast resonant frequency.
Prior systems often require dynamic seals against translation and rotation at the mast hull penetration fitting, increasing the maintenance and reliability problems associated therewith. Such seals are very difficult to access and replace while at sea. Additionally, such seals tend to utilize design concepts that are compromises between the rotational and translational motions that the seal should withstand. Generally, repairs of such seals are effected in dry dock where the mast mechanism can be removed therefrom.
Typically, the submarine sail mount stations are utilized for providing support for the mast system. In prior designs these supports are required to accommodate translation and rotation of the mast with the concomitant problems associated therewith. In such prior systems critical components are often included at these stations and hence are exposed to sea water.